The present invention relates to an apparatus for distributing a liquid in a patient's body, wherein the apparatus includes an implantable valve pump assembly for pumping the liquid. The invention also relates to a valve device of the apparatus particularly suited for implantation in the patient's body to direct the liquid. The term “patient” includes a human being or animal.
There are many important requirements for a valve pump assembly that is suited for implantation in the human body. The valve pump assembly should be small, often be capable of generating two to three bars of pressure, have a sufficient flow capacity, sometimes in the order of two to three ml per minute, and, above all, consume little energy so that, for example, an implanted battery powering the assembly will last for a long time. Many of the above requirements are contradictory. Existing small pumps generally have a too low pressure capability, a too low flow capacity and a too high energy consumption to be suited for implantation in a human body.
Another important requirement for an implantable pump, which to some extent is related to the consumption of current, is that the amount of heat that the pump generates during operation should be low. Legally, an implant is not allowed to increase the temperature inside a human body by more than 3° C., ice., from 37° to 40° C. Thus, it is very important that the energy loss of the pump that generates heat be very low.
Another important requirement for an implantable valve pump assembly is that no leakage or diffusion of liquid should occur when the implanted assembly has not been operated for a long period of time. A traditional valve of prior valve pump assemblies, typically a non-return valve, works nicely when pressure is prevailing in the hydraulic channels of the valve. In an implanted valve, however, the pressure can at times be zero, which would make it very difficult to keep the valve properly working over a long period of time. Even more important is the long term diffusion which occurs across nearly all kinds of polymer or plastic material over a long period of time.
A further important requirement for an implantable valve pump assembly is that the pump should be capable of pumping in different directions without risking deterioration of the function of the valve over time. For example, the valve might become clogged or might stop working after not operating for a long period of time in a temperature of 37° C.